Synchronization of mobility management data between a circuit-switched domain and a packet-switched domain

ABSTRACT

Systems and methods for synchronizing mobility management (MM) data between a CS domain and a PS domain. In one embodiment, a visitor location database of the CS domain stores MM data for a mobile device. If the visitor location database updates MM data for the mobile device to add an association for an MM node for mobility management, then the visitor location database determines if a prior association existed with another MM node. If so, the visitor location database removes the prior association with the other MM node, and transmits a release indicator to the other MM node indicating that the association has been removed. In response to the release indicator, the other MM node removes an association with the visitor location database, and the MM data for the mobile device is synchronized between the CS domain and the PS domain.

FIELD OF THE INVENTION

The invention is related to the field of communications and, inparticular, to synchronizing data between a Circuit Switched (CS) domainand a Packet-Switched (PS) domain.

BACKGROUND

Service providers typically offer numerous voice and data services toend users. Some examples of voice services are voice calls, callforwarding, call waiting, etc. Some examples of data services areInternet access, streaming audio, streaming video, online gaming, IP-TV,etc.

The first types of wireless or mobile networks that were introduced byservices providers were First Generation (1G) and Second Generation (2G)networks. 1G networks provided voice services via analog signals, andthen evolved into 2G networks that provided voice services via digitalsignals. Mobile communications then evolved into 3G (including 2.5G)networks that provided both voice services and data services. Forexample, 3G networks are able to provide wireless voice telephony, aswell as data services such as Internet access, video calls, mobile TV,etc. Some of the 3G networks implemented by service providers wereUniversal Mobile Telecommunications System (UMTS) networks, EV-DOnetworks, General Packet Radio Service (GPRS) networks, etc. Serviceproviders are now beginning to migrate their networks toward FourthGeneration (4G) technologies. 4G networks are essentially enhancementsto 3G networks in terms of data speeds. For example, a 3G network canprovide data speeds of about 3.5 Mbit/sec. According to theInternational Telecommunication Union (ITU), a 4G network can providedata speeds of 100 Mbit/sec. One example of a 4G network is a Long TermEvolution (LTE) network.

Presently, 4G communications are available in limited areas, such aslarge cities. When a mobile device is in the coverage area of a 4Gnetwork, the mobile device is able to attach to the 4G network toreceive services. When a 4G network is not available, the mobile devicemay be in the coverage area of a 3G (or 2G) network in many cases. Thus,the mobile device can register with the 3G network to receive services.Mobile devices that are able to register with both 4G and 3G networksmay be referred to as dual mode or multi-mode devices.

Early implementations of 4G networks provide data services but do notprovide voice services for mobile devices (assuming VoIP services arenot available through the IP Multimedia Subsystem (IMS)). Therefore, inorder for the mobile device to place or receive voice calls, the mobiledevice needs to also attach to a Circuit-Switched (CS) core network (2Gor 3G) to access voice services. The CS core network that provides voiceservices is referred to as the CS domain, while the data portion of a 3Gor 4G network that provides data services is referred to as thePacket-Switched (PS) domain. When a mobile device switches from a 4Gnetwork to a CS core network to originate or terminate voice calls, thisis referred to as “CS Fallback”.

In order to serve a mobile device, the CS domain and the PS domainperform mobility management procedures such as attach, paging, andlocation update procedures. The attach procedure is a process that amobile device performs to register with a network before the mobiledevice can access services. The paging procedure is a process where thenetwork contacts the mobile device using control messages. Locationupdate is a procedure where the location of a mobile device is reportedto the network.

Both the CS domain and the PS domain store a Mobility Management (MM)context for a mobile device, which indicates the mobility informationfor the device. For example, the MM context for a mobile device mayinclude an International Mobile Subscriber Identity (IMSI), a MM state,a Temporary Mobile Subscriber Identity (TMSI or P-TMSI), a location areaor routing area, a Mobile Station ISDN Number (MSISDN), cipheringalgorithms, etc. Most networks allow a mobile device to simultaneouslyconnect to the CS domain and the PS domain, which is sometimes referredto as a Class A operation mode or PS/CS operation mode. When a mobiledevice is allowed to simultaneously attach to the CS domain and the PSdomain, MM data can become desynchronized across the CS and PS domains.If MM data is not synchronized, mobility management procedures may notbe performed correctly. For example, paging procedures to the mobiledevice may not be performed correctly if the MM data is not synchronizedbetween the CS and PS domains.

SUMMARY

Embodiments described herein synchronize Mobility Management (MM) databetween the CS domain and the PS domain through a visitor locationdatabase implemented in the CS domain. Before discussing how the visitorlocation database synchronizes the MM data, the following brieflysummarizes how MM data can become desynchronized. The visitor locationdatabase is a node in the CS domain that maintains MM data for a mobiledevice. The visitor location database interacts with the PS domain totrack the location of the mobile device if the mobile device attaches toa PS data network. If the mobile device attaches to a PS data network,then a Mobility Management (MM) node in the PS data network sends alocation update to the visitor location database to establish asignaling connection with the CS domain. A MM node comprises any networknode in the PS domain that tracks the location of a mobile device. Whenthe visitor location database receives a location update from a MM nodein the PS domain, it updates the MM data for the mobile device toactivate an “association” with the MM node for the purpose of mobilitymanagement. For example, the visitor location database may add anidentifier (ID) for the MM node into a location register for the mobiledevice. If a prior association existed with another MM node from the PSdomain, then the visitor location database deactivates the priorassociation with the other MM node from the location register of themobile device. Even though the visitor location database has deactivatedthe prior association with the other MM node, that MM node is not awareof the signaling connection changes at the visitor location database andcontinues to store MM data for the mobile device indicating anassociation with the visitor location database. When this occurs, the MMdata for the mobile device is no longer synchronized between the CSdomain (i.e., the visitor location database) and the PS domain (i.e.,the other MM node).

In the embodiments described herein, the visitor location databasenotifies the other MM node that the association with the other MM nodehas been deactivated in the location register of the mobile device.Therefore, the other MM node can update its local MM data for the mobiledevice to indicate that its association with the visitor locationdatabase is likewise deactivated. When this MM node updates the MM datafor the mobile device in response to the notification from the visitorlocation database, the MM data for the mobile device is advantageouslysynchronized between the CS domain and the PS domain. Mobilitymanagement procedures for the mobile device will therefore be performedcorrectly.

One embodiment comprises a visitor location database of a CS domain. Thevisitor location database is configured to communicate with a first MMnode of a first PS data network that connects to the mobile device inthe PS domain. The visitor location database is configured to store MMdata for the mobile device that indicates an association with the firstMM node. If the mobile device moves from the first PS data network to asecond PS data network, then the visitor location database is furtherconfigured to update the MM data for the mobile device to remove theassociation with the first MM node. The visitor location database isfurther configured to generate a release indicator which indicates thatthe association with the first MM node has been removed, and to transmitthe release indicator to the first MM node so that the first MM nodereleases an association with the visitor location database from the MMdata stored for the mobile device.

In another embodiment, the visitor location database is furtherconfigured to update the MM data for the mobile device to add anassociation with a second MM node of the second PS data network inresponse to the mobile device moving from the first PS data network tothe second PS data network.

In another embodiment, the first MM node comprises a Serving GPRSSupport Node (SGSN) of a General Packet Radio Service (GPRS) network,and the SGSN connects to the visitor location database over a Gsinterface. The visited location database is further configured to insertthe release indicator in a new Information Element (IE) of a messagedefined for the Gs interface.

In another embodiment, the message defined for the Gs interfacecomprises a Gs-RELEASE-REQUEST.

In another embodiment, the first MM node comprises a Mobility ManagementEntity (MME) of a Long Term Evolution (LTE) network, and the MMEconnects to the visitor location database over an SGs interface. Thevisited location database is further configured to insert the releaseindicator in a new Information Element (IE) of a message defined for theSGs interface.

In another embodiment, the message defined for the SGs interfacecomprises an SGs-RELEASE-REQUEST.

In another embodiment, the visitor location database comprises a VisitorLocation Register (VLR) of the CS domain.

Another embodiment comprises a method operable in a visitor locationdatabase of a CS domain. The visitor location database is configured tocommunicate with a first MM node of a first PS data network thatconnects to the mobile device in a PS domain, and to communicate with asecond MM node of a second PS data network that connects to the mobiledevice in the PS domain. The method includes storing MM data for themobile device that indicates an association with the first MM node. Ifthe mobile device moves from the first PS data network to the second PSdata network, then the method further includes updating the MM data forthe mobile device to remove the association with the first MM node,generating a release indicator which indicates that the association withthe first MM node has been removed, and transmitting the releaseindicator to the first MM node so that the first MM node releases anassociation with the visitor location database from the MM data storedfor the mobile device.

In another embodiment, the method further includes updating the MM datafor the mobile device to add an association with a second MM node of thesecond PS data network in response to the mobile device moving from thefirst PS data network to the second PS data network.

In another embodiment, the first MM node comprises a Serving GPRSSupport Node (SGSN) of a General Packet Radio Service (GPRS) network,and the SGSN connects to the visitor location database over a Gsinterface. The method further includes inserting the release indicatorin a new Information Element (IE) of a message defined for the Gsinterface.

In another embodiment, the message defined for the Gs interfacecomprises a Gs-RELEASE-REQUEST.

In another embodiment, the first MM node comprises a Mobility ManagementEntity (MME) of a Long Term Evolution (LTE) network, and the MMEconnects to the visitor location database over an SGs interface. Themethod further includes inserting the release indicator in a newInformation Element (IE) of a message defined for the SGs interface.

In another embodiment, the message defined for the SGs interfacecomprises an SGs-RELEASE-REQUEST.

In another embodiment, the visitor location database comprises a VisitorLocation Register (VLR) of the CS domain.

Another embodiment comprises a Visitor Location Register (VLR) of aCircuit-Switched (CS) domain that is able to provide voicecommunications to a mobile device. The VLR is configured to communicatewith a Serving GPRS Support Node (SGSN) of a General Packet RadioService (GPRS) network over a Gs interface, and to communicate with aMobility Management Entity (MME) of a Long Term Evolution (LTE) networkover an SGs interface. If the mobile device attaches to the GPRS networkafter initially attaching to the LTE network, then the VLR is furtherconfigured to update MM data for the mobile device to activate a Gsassociation with the SGSN, and to update the MM data for the mobiledevice to deactivate an SGs association with the MME. The VLR is furtherconfigured to generate a release indicator which indicates that the SGsassociation is deactivated in the VLR, and to transmit the releaseindicator to the MME over the SGs interface.

In another embodiment, the VLR is further configured to insert therelease indicator in a new Information Element (IE) of a message definedfor the SGs interface.

In another embodiment, the message defined for the SGs interfacecomprises an SGs-RELEASE-REQUEST.

In another embodiment, if the mobile device attaches to the LTE networkafter initially attaching to the GPRS network, then the VLR is furtherconfigured to update MM data for the mobile device to activate an SGsassociation with the MME, and to update the MM data for the mobiledevice to deactivate a Gs association with the SGSN. The VLR is furtherconfigured to generate a release indicator which indicates that the Gsassociation is deactivated in the VLR, and to transmit the releaseindicator to the SGSN over the Gs interface.

In another embodiment, the VLR is further configured to insert therelease indicator in a new Information Element (IE) of a message definedfor the Gs interface.

In another embodiment, the message defined for the Gs interfacecomprises a Gs-RELEASE-REQUEST.

Other exemplary embodiments may be described below.

DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are now described, by way ofexample only, and with reference to the accompanying drawings. The samereference number represents the same element or the same type of elementon all drawings.

FIG. 1 illustrates a network architecture in an exemplary embodiment.

FIG. 2 is a message diagram illustrating Mobility Management (MM) databecoming desynchronized between a CS domain and a PS domain in anexemplary embodiment.

FIG. 3 is a flow chart illustrating a method of synchronizing MM data inan exemplary embodiment.

FIG. 4 is a message diagram illustrating MM data becoming synchronizedin an exemplary embodiment.

FIG. 5 illustrates another network architecture in an exemplaryembodiment.

FIGS. 6-7 are message diagrams illustrating a VLR synchronizing MM datain an exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

The figures and the following description illustrate specific exemplaryembodiments of the invention. It will thus be appreciated that thoseskilled in the art will be able to devise various arrangements that,although not explicitly described or shown herein, embody the principlesof the invention and are included within the scope of the invention.Furthermore, any examples described herein are intended to aid inunderstanding the principles of the invention, and are to be construedas being without limitation to such specifically recited examples andconditions. As a result, the invention is not limited to the specificembodiments or examples described below, but by the claims and theirequivalents.

FIG. 1 illustrates a network architecture 100 in an exemplaryembodiment. Network architecture 100 includes a plurality of networksthat are able to provide services to a mobile device 150 (also referredto as User Equipment (UE)). The first network shown is Circuit-Switched(CS) voice network 110 that is configured to provide traditional voiceservices to mobile device 150 through Radio Access Network (RAN) 116. CSvoice network 110 may also be referred to herein as the CS domain. Someexamples of CS voice network 110 may be a GSM network, a CDMA2000network, etc. In this embodiment, CS voice network 110 includes aswitching node 112 (such as a Mobile Switching Center (MSC)), and avisitor location database 114. Visitor location database 114 comprisesany network node that stores information, such as a location register,regarding subscribers that are located in an area served by switchingnode 112. One example of visitor location database 114 is a VisitorLocation Register (VLR). Although switching node 112 and visitorlocation database 114 are shown as separate elements, visitor locationdatabase 114 may be integrated within switching node 112. CS voicenetwork 110 may also include other network nodes that are not shown inFIG. 1, such as a Home Location Register (HLR).

The second network shown in FIG. 1 is a Packet-Switched (PS) datanetwork 120, which is configured to provide data services to mobiledevice 150 through RAN 126. PS data network 120 may be referred hereinas the PS domain. Some examples of PS data network 120 may be a GPRSnetwork, a UMTS network, etc. PS data network 120 includes a MobilityManagement (MM) node 122, which comprises any network node in the PSdomain that tracks the location of mobile device 150 so that servicesmay be provided to mobile device 150. One example of MM node 122 is aServing GPRS Support Node (SGSN) of a GPRS network. PS data network 120may include other network nodes that are not shown in FIG. 1.

The third network shown in FIG. 1 is another PS data network 130 that isalso part of the PS domain, and is configured to provide data servicesto mobile device 150 through RAN 136. The assumption herein is that PSdata network 120 and PS data network 130 are different technologynetworks that are available to mobile device 150. For example, PS datanetwork 120 may represent a 2.5G or 3G data network that a serviceprovider has implemented to offer data services to its subscribers, suchas a GPRS network. As the service provider migrates its networkarchitecture to include 4G technologies, then PS data network 130 mayrepresent the 4G portion of the network architecture that is overlaid onthe 3G data network. For example, PS data network 130 may be a Long TermEvolution (LTE) network. In this embodiment, PS data network 130 alsoincludes a Mobility Management (MM) node 132. One example of MM node 132is a Mobility Management Entity (MME) of an LTE network. PS data network130 may include other network nodes that are not shown in FIG. 1.

Although PS data networks 120 and 130 are able to provide data servicesto mobile device 150, the assumption herein is that they do not providevoice services to mobile device 150. The voice services for mobiledevice 150 are handled by CS voice network 110. Anytime a voice call isreceived for mobile device 150, PS data networks 120 and 130 “fallback”to CS voice network 110 to complete the call. In order to allow forfallback to CS voice network 110, the CS domain needs to know wheremobile device 150 is located in the network. Thus, PS data networks 120and 130 exchange mobility management (MM) data with the CS domain sothat the location of mobile device 150 is known. To exchange MM data, MMnode 122 communicates with visitor location database 114 over interface128, while MM node 132 communicates with visitor location database 114over interface 138. If MM node 122 represents an SGSN of a GPRS network,then interface 128 may comprise a Gs interface. If MM node 132represents an MME of an LTE network, then interface 138 may comprise anSGs interface.

Visitor location database 114 stores MM data for mobile device 150, suchas in a location register for mobile device 150. The MM data may also bereferred to as an MM context. One particular piece of information storedfor an MM context of a mobile device is an identifier (ID) or some otherinformation for an MM node in the PS domain that is connected to mobiledevice 150. For example, if mobile device 150 attaches to PS datanetwork 120, then MM node 122 will be “connected” to mobile device 150for mobility management. Thus, visitor location database 114 will storean ID for MM node 122 so that it knows which node to contact formobility management. When visitor location database 114 stores an ID foran MM node in this manner, it is referred to as an “association”. Anassociation is considered a relationship or path between an entity ofthe CS domain and an entity of the PS domain for mobility management.For example, if MM node 122 comprises an SGSN of a GPRS network, thenvisitor location database 114 will store an “SGSN association” or a “Gsassociation”, which indicates the SGSN that is providing mobilitymanagement for mobile device 150 over a Gs interface.

At the same time that visitor location database 114 stores an MM contextfor mobile device 150, MM nodes 122 and 132 may also store an MM contextfor mobile device 150 in location register. One particular piece ofinformation stored for an MM context in an MM node is an ID or someother information for the visitor location database in the CS domain.Thus, MM node 122, for example, will store an ID for visitor locationdatabase 114 so that it knows which node in the CS domain to contact formobility management. When MM node 122 stores an ID for visitor locationdatabase 114 in this manner, it is also referred to as an “association”.For example, if visitor location database 114 comprises a VLR, then MMnode 122 will store a VLR association which indicates the VLR that isproviding mobility management for mobile device 150 in the CS domain.

With MM data being stored both in the CS domain and the PS domain, it isimportant to make sure that the MM data is synchronized between thedomains. However, there are scenarios where the MM data can becomedesynchronized between the domains, as is described in FIG. 2.

FIG. 2 is a message diagram illustrating MM data becoming desynchronizedin an exemplary embodiment. Assume for example that mobile device 150sends a combined PS/CS attach request (or update request) to MM node122. In response to the combined PS/CS attach request, MM node 122 sendsa location update request to visitor location database 114 with thelocation area or routing area where mobile device 150 is located. Inresponse to the location update, visitor location database 114 adds oractivates an association for MM node 122 in the MM context for mobiledevice 150, such as by storing an ID for MM node 122 in a locationregister for mobile device 150. MM node 122 is therefore “associated”with visitor location database 114 for mobile device 150 (MM node 132 is“associated—NULL”). Visitor location database 114 then responds back toMM node 122 with a location update answer. MM node 122 adds or activatesan association for visitor location database 114 in the MM context formobile device 150, such as by storing an ID for visitor locationdatabase 114 in a location register for mobile device 150. Visitorlocation database 114 is therefore “associated” with MM node 122 formobile device 150.

Assume further that mobile device 150 moves from the service area of PSdata network 120 to the service area of PS data network 130. When thisoccurs, mobile device 150 will send combined a PS/CS attach request toMM node 132 of PS data network 130. Mobile device 150 cannot besimultaneously attached to both PS data networks, so mobile device 150will also detach from PS data network 120 (which is not shown in FIG.2). When MM node 132 receives the combined PS/CS attach request, itsends a location update request to visitor location database 114 withthe location area or routing area where mobile device 150 is located. Inresponse to the location update, visitor location database 114 adds oractivates an association for MM node 132 in the MM context for mobiledevice 150. In the CS domain, activation of one association will triggerdeactivation of another association. Thus, visitor location database 114will remove the prior association with MM node 122 from the locationregister of mobile device 150. MM node 132 is now indicated in visitorlocation database 114 as “associated” for mobile device 150 (MM node 122is “associated—NULL”). Visitor location database 114 then responds backto MM node 132 with a location update answer. MM node 132 adds anassociation for visitor location database 114 in the MM context formobile device 150, such as by storing an ID for visitor locationdatabase 114. Visitor location database 114 is therefore associated withMM node 132 for mobile device 150.

After mobile device 150 attaches to PS data network 130, the MM data inthe CS domain is no longer synchronized with the PS domain. Visitorlocation database 114 indicates an association with MM node 132, and MMnode 132 indicates an association with visitor location database 114.However, MM node 122 also indicates an association with visitor locationdatabase 114, but visitor location database 114 no longer has anassociation with MM node 122. After mobile device 150 moves from PS datanetwork 120 and attaches to PS data network 130, there is no longer anassociation between MM node 122 and visitor location database 114. Thus,MM node 122 is storing incorrect MM data for mobile device 150, and theMM data for mobile device 150 is no longer synchronized between the CSdomain and the PS domain.

In the embodiments described herein, visitor location database 114 of CSvoice network 110 is enhanced to synchronize MM data between the CSdomain and PS domain. An exemplary operation of visitor locationdatabase 114 for synchronizing MM data is described in FIG. 3

FIG. 3 is a flow chart illustrating a method 300 of synchronizing MMdata in an exemplary embodiment. The steps of method 300 will bedescribed with reference to visitor location database 114 in FIG. 1, butthose skilled in the art will appreciate that method 300 may beperformed in other nodes. The steps of the flow charts described hereinare not all inclusive and may include other steps not shown. The stepsmay also be performed in an alternative order.

Assume again that mobile device 150 was attached to PS data network 120and moves to PS data network 130 as shown in FIG. 2. MM node 132receives the combined PS/CS attach request from mobile device 150, andsends a location update request to visitor location database 114.Visitor location database 114 receives the location update request fromMM node 132 indicating that mobile device 150 is connected (or hasattached) to the MM node 132. In response to the location updaterequest, visitor location database 114 updates the MM data in thelocation register for mobile device 150. To do so, visitor locationdatabase 114 adds or activates an association with MM node 132 that ispresently connected to mobile device 150 (see step 302 in FIG. 3). Forexample, visitor location database 114 may add or store an ID for MMnode 132 in the location register for mobile device 150 to indicate thatmobile device 150 is connected to MM node 132 of the PS domain. Visitorlocation database 114 also determines if a prior association exists withanother MM node in step 304. For example, visitor location database 114may search the location register for mobile device 150 to see if an IDfor another MM node has been stored. If so, visitor location database114 updates the MM data for mobile device 150 to remove or deactivatethe prior association with the other MM node in step 306. For example,visitor location database 114 may remove or delete an ID for MM node 122in the location register for mobile device 150 to indicate that mobiledevice 150 is no longer connected to mobile device 150. Thus, the MMdata stored in visitor location database 114 will indicate anassociation with MM node 132 and no association with MM node 122.

If visitor location database 114 removes a prior association withanother MM node from the location register of mobile device 150, thenvisitor location database 114 will notify the other MM node according tomethod 300. To do so, visitor location database 114 generates a releaseindicator which indicates that the prior association with the other MMnode has been removed from the location register for mobile device 150(see step 308). The release indicator comprises any data, field, orparameter that notifies or informs an MM node when an association hasbeen removed from visitor location database 114. The release indicatormay additionally or alternatively include a command or instruction forthe MM node to remove a corresponding association from the MM data thatit stores locally for mobile device 150. The indicator is referred to asa “release” indicator because the MM node is requested to release itsassociation with visitor location database 114 due to the changes madein the location register of visitor location database 114.

Visitor location database 114 then transmits the release indicator tothe MM node in step 310, which is MM node 122. Visitor location database114 may insert the release indicator into an existing message definedfor the interface used by MM node 122. For example, if the interfacebetween visitor location database 114 and MM node 122 is a Gs interface,then visitor location database 114 may insert the release indicator intoa Gs-RELEASE-REQUEST. A new Information Element (IE) may be defined inthe Gs interface for the release indicator. If the interface betweenvisitor location database 114 and MM node 122 is an SGs interface, thenvisitor location database 114 may insert the release indicator into anSGs-RELEASE-REQUEST. A new IE may be defined in the SGs interface forthe release indicator. Visitor location database 114 may also define anew message for the release indicator.

In response to receiving the release indicator, MM node 122 releases theassociation with visitor location database 114 from the MM data storedfor mobile device 150. For example, visitor location database 114 mayremove the ID for visitor location database 114 from the MM data storedfor mobile device 150. After MM node 122 removes the association withvisitor location database 114, the MM data for mobile device 150 issynchronized between the CS domain and the PS domain.

FIG. 4 is a message diagram illustrating MM data becoming synchronizedin an exemplary embodiment. FIG. 4 is similar to FIG. 2, except thanwhen visitor location database 114 removes the prior association with MMnode 122 from the location register of mobile device 150, visitorlocation database 114 sends the release indicator to MM node 122. Inresponse to receiving the release indicator, MM node 122 releases theassociation with visitor location database 114 from the MM data storedfor mobile device 150. Therefore, the MM data for mobile device 150 isnow synchronized between the CS domain and the PS domain.

To summarize method 300, when visitor location database 114 updates theMM context for mobile device 150 to remove an association with an MMnode, visitor location database 114 notifies this MM node of thedisassociation using a release indicator. The MM node can then removeits association with visitor location database 114 so that the MM datafor mobile device 150 is synchronized between the CS domain and the PSdomain. Previously, the MM node would maintain its association withvisitor location database 114 even though mobile device 150 attached toanother network. This can be problematic to mobility managementprocedures, such as paging. The enhancements to visitor locationdatabase 114 as described herein advantageously synchronize MM databetween the CS domain and the PS domain to avoid such problems.

Example

FIG. 5 illustrates a network architecture 500 in another exemplaryembodiment. Network architecture 500 includes a CS voice network 510that represents a CS domain. Voice network 510 may comprise a GSM,CDMA2000, or another type of voice network that includes an MobileSwitching Center (MSC) 512 and a Visitor Location Register (VLR) 514.Those skilled in the art understand that MSC 512 and VLR 514 may beintegrated together. CS voice network 510 is able to provide voiceservices to User Equipment (UE) 550 over a Radio Access Network (RAN)516.

Network architecture 500 also includes a 3G (or 2.5G) data network 520.3G data network 520 in this example is a GPRS network that is able toprovide data services to UE 550. The GPRS network includes an SGSN 522that is responsible for exchanging packets with UE 550 over RAN 526.Another responsibility of SGSN 522 is mobility management for UE 550.SGSN 522 includes a location register (not shown) which storesinformation for UE 550, such as location information, the present VLRfor UE 550, user profiles, etc. In order to perform mobility management,SGSN 522 communicates with VLR 514 over a Gs interface.

Network architecture 500 also includes a 4G data network 530. 4G datanetwork 530 in this example is an LTE network that is able to providedata services to UE 550. The LTE network includes an MME 532 that isresponsible for mobility management for UE 550. MME 532 also includes alocation register (not shown) which stores information for UE 550, suchas location information, the present VLR for UE 550, etc. In order toperform mobility management, MME 532 communicates with VLR 514 over anSGs interface.

Both 3G data network 520 and 4G data network 530 may include additionalnetwork nodes, but the relevant nodes are shown in FIG. 5.

In this example, VLR 514 is enhanced so that it synchronizes MM data forUE 550 between the CS domain and the PS domain. The PS domain in thisexample is represented by the GPRS network (i.e., 3G data network 520)and the LTE network (i.e., the 4G data network 530).

FIG. 6 is a message diagram illustrating VLR 514 synchronizing MM datain an exemplary embodiment. In this example, UE 550 is initiallyattached to the GPRS network through SGSN 522. Therefore, the locationregister for UE 550 as stored locally in SGSN 522 indicates anassociation with VLR 514. When SGSN 522 has an association with VLR 514over the Gs interface, SGSN 522 stores a status of “Gs associated” inthe location register for UE 550. Also, VLR 514 has an association withSGSN 522 for UE 550. Thus, VLR 514 stores a status of “Gs associated” inthe location register for UE 550.

After attaching to the GPRS network, UE 550 moves to a service areaserved by the LTE network. When this occurs, UE 550 sends a combinedEPS/IMSI attach request to MME 532 to attach to the LTE network. MME 532then sends a LOCATION-UPDATE-REQUEST to VLR 514 over the SGs interface.When VLR 514 receives the LOCATION-UPDATE-REQUEST, VLR 514 updates theMM data for UE 550. Gs and SGs associations cannot be activesimultaneously in VLR 514 for a UE. On the VLR side, activation of oneassociation would trigger deactivation of the other association. Thus,VLR 514 adds an indicator of an SGs association with MME 532 in the MMcontext for UE 550 to activate the SGs association. The locationregister in VLR 514 will therefore indicate a status of “SGs associated”for UE 550.

If VLR 514 changes the association status the location register of UE550, it will also determine if a prior association existed. In thiscase, a prior association existed with SGSN 522 as a Gs association. Ifthe Gs association is not NULL, then VLR 514 will reset the status to“Gs-NULL”. At this point, the MM context for UE 550 in VLR 514 willindicate an SGs association with MME 532, and no Gs association withSGSN 522.

Even though VLR 514 has removed the Gs association, SGSN 522 stillindicates a Gs association is active with VLR 514 for UE 550. In orderto synchronize the MM data with the PS domain, VLR 514 generates arelease indicator that is intended for SGSN 522. The release indicatorindicates to SGSN 522 that the Gs association on the VLR side has beenremoved because UE 550 has attached to another network. Therefore, SGSN522 needs to deactivate or release the Gs association with VLR 514 forUE 550. VLR 514 inserts the release indicator in a message, such as aGs-RELEASE-REQUEST, and sends the Gs-RELEASE-REQUEST to SGSN 522. WhenSGSN 522 receives the Gs-RELEASE-REQUEST (with the cause indicating“release Gs”), SGSN 522 removes the Gs association for UE 550 from itslocation register and sets the Gs association status to “Gs-NULL”. Atthis point, the MM data is synchronized between the PS domain and the CSdomain.

FIG. 7 is a message diagram illustrating another example of VLR 514synchronizing MM data in an exemplary embodiment. In this example, UE550 is attached to the LTE network. Therefore, the location register forUE 550 as stored locally in MME 532 indicates an association with VLR514. When MME 532 has an association with VLR 514 over the SGsinterface, MME 532 stores a status of “SGs associated” in the locationregister for UE 550. Also, VLR 514 indicates in its locally-stored MMcontext for UE 550 that there is an association with MME 532. Thus, VLR514 stores a status of “SGs associated” in the location register for UE550.

After attaching to the LTE network, UE 550 moves to a service area ofthe GPRS network. When this occurs, UE 550 sends a combined GPRS/IMSIattach request to SGSN 522 to attach to the GPRS network. SGSN 522 thensends a LOCATION-UPDATE-REQUEST to VLR 514 over the Gs interface. WhenVLR 514 receives the LOCATION-UPDATE-REQUEST, VLR 514 updates the MMdata for UE 550. To do so, VLR 514 adds an indicator of a Gs associationwith SGSN 522 in the MM context for UE 550 to activate the Gsassociation. The location register in VLR 514 will therefore indicate astatus of “Gs associated” for UE 550.

If VLR 514 changes the association status the location register of UE550, it will also determine if a prior association existed. In thiscase, a prior association existed with MME 532 as an SGs association. Ifthe SGs association is not NULL, then VLR 514 will reset the status to“SGs-NULL”. At this point, the MM context for UE 550 in VLR 514 willindicate a Gs association with SGSN 522, and no SGs association with MME532.

Even though VLR 514 has removed the SGs association, MME 532 stillindicates an SGs association is active with VLR 514 for UE 550. In orderto synchronize the MM data with the PS domain, VLR 514 generates arelease indicator that is intended for MME 532. The release indicatorindicates to MME 532 that the SGs association on the VLR side has beenremoved because UE 550 has attached to another network. Therefore, MME532 needs to deactivate or release the SGs association with VLR 514 forUE 550. VLR 514 inserts the release indicator in a message, such as anSGs-RELEASE-REQUEST, and sends the SGs-RELEASE-REQUEST to MME 532. WhenMME 532 receives the SGs-RELEASE-REQUEST (with the cause indicating“release SGs”), MME 532 removes the SGs association for UE 550 and setsthe SGs association status to “SGs-NULL”. At this point, the MM data forUE 550 is synchronized between the PS domain and the CS domain.

Any of the various elements shown in the figures or described herein maybe implemented as hardware, software, firmware, or some combination ofthese. For example, an element may be implemented as dedicated hardware.Dedicated hardware elements may be referred to as “processors”,“controllers”, or some similar terminology. When provided by aprocessor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. Moreover, explicit use of theterm “processor” or “controller” should not be construed to referexclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, a network processor, application specific integrated circuit(ASIC) or other circuitry, field programmable gate array (FPGA), readonly memory (ROM) for storing software, random access memory (RAM),non-volatile storage, logic, or some other physical hardware componentor module.

Also, an element may be implemented as instructions executable by aprocessor or a computer to perform the functions of the element. Someexamples of instructions are software, program code, and firmware. Theinstructions are operational when executed by the processor to directthe processor to perform the functions of the element. The instructionsmay be stored on storage devices that are readable by the processor.Some examples of the storage devices are digital or solid-statememories, magnetic storage media such as a magnetic disks and magnetictapes, hard drives, or optically readable digital data storage media.

Although specific embodiments were described herein, the scope of theinvention is not limited to those specific embodiments. The scope of theinvention is defined by the following claims and any equivalentsthereof.

I claim:
 1. A system comprising: a visitor location database of aCircuit-Switched (CS) domain that is able to provide voicecommunications to a mobile device; the visitor location database isconfigured to communicate with a first Mobility Management (MM) node ofa first Packet-Switched (PS) data network that connects to the mobiledevice in a PS domain; the visitor location database is furtherconfigured to store MM data for the mobile device that indicates anassociation with the first MM node; the visitor location database isfurther configured to, in response to determining the mobile devicemoves from the first PS data network to a second PS data network, updatethe MM data for the mobile device to remove the association with thefirst MM node, generate a release indicator which indicates that theassociation with the first MM node has been removed, and transmit therelease indicator to the first MM node so that the first MM nodereleases an association with the visitor location database from the MMdata stored for the mobile device.
 2. The system of claim 1 wherein: thevisitor location database is further configured to update the MM datafor the mobile device to add an association with a second MM node of thesecond PS data network in response to determining the mobile devicemoves from the first PS data network to the second PS data network. 3.The system of claim 1 wherein: the first MM node comprises a ServingGPRS Support Node (SGSN) of a General Packet Radio Service (GPRS)network, and the SGSN connects to the visitor location database over aGs interface; the visited location database is further configured toinsert the release indicator in a new Information Element (IE) of amessage defined for the Gs interface.
 4. The system of claim 3 wherein:the message defined for the Gs interface comprises a Gs-RELEASE-REQUEST.5. The system of claim 1 wherein: the first MM node comprises a MobilityManagement Entity (MME) of a Long Term Evolution (LTE) network, and theMME connects to the visitor location database over an SGs interface; thevisited location database is further configured to insert the releaseindicator in a new Information Element (IE) of a message defined for theSGs interface.
 6. The system of claim 5 wherein: the message defined forthe SGs interface comprises an SGs-RELEASE-REQUEST.
 7. The system ofclaim 1 wherein: the visitor location database comprises a VisitorLocation Register (VLR) of the CS domain.
 8. A method operable in avisitor location database of a Circuit-Switched (CS) domain that is ableto provide voice communications to a mobile device, wherein the visitorlocation database is configured to communicate with a first MobilityManagement (MM) node of a first Packet-Switched (PS) data network thatconnects to the mobile device in a PS domain, and to communicate with asecond MM node of a second PS data network that connects to the mobiledevice in the PS domain, the method comprising: storing MM data for themobile device that indicates an association with the first MM node;after determining the mobile device moves from the first PS data networkto the second PS data network, then: updating the MM data for the mobiledevice to remove the association with the first MM node; generating arelease indicator which indicates that the association with the first MMnode has been removed; and transmitting the release indicator to thefirst MM node for instructing the first MM node to release anassociation with the visitor location database from the MM data storedfor the mobile device.
 9. The method of claim 8 further comprising:updating the MM data for the mobile device to add an association with asecond MM node of the second PS data network in response to determiningthe mobile device moves from the first PS data network to the second PSdata network.
 10. The method of claim 8 wherein: the first MM nodecomprises a Serving GPRS Support Node (SGSN) of a General Packet RadioService (GPRS) network, and the SGSN connects to the visitor locationdatabase over a Gs interface; and the method further comprises:inserting the release indicator in a new Information Element (IE) of amessage defined for the Gs interface.
 11. The method of claim 10wherein: the message defined for the Gs interface comprises aGs-RELEASE-REQUEST.
 12. The method of claim 8 wherein: the first MM nodecomprises a Mobility Management Entity (MME) of a Long Term Evolution(LTE) network, and the MME connects to the visitor location databaseover an SGs interface; and the method further comprises: inserting therelease indicator in a new Information Element (IE) of a message definedfor the SGs interface.
 13. The method of claim 12 wherein: the messagedefined for the SGs interface comprises an SGs-RELEASE-REQUEST.
 14. Themethod of claim 8 wherein: the visitor location database comprises aVisitor Location Register (VLR) of the CS domain.
 15. A systemcomprising: a Visitor Location Register (VLR) of a Circuit-Switched (CS)domain that is able to provide voice communications to a mobile device;the VLR is configured to communicate with a Serving GPRS Support Node(SGSN) of a General Packet Radio Service (GPRS) network over a Gsinterface, and to communicate with a Mobility Management Entity (MME) ofa Long Term Evolution (LTE) network over an SGs interface; the VLR isfurther configured to, in response to determining the mobile deviceattaches to the GPRS network after initially attaching to the LTEnetwork, update MM data for the mobile device to activate a Gsassociation with the SGSN, and update the MM data for the mobile deviceto deactivate an SGs association with the MME; the VLR is furtherconfigured to generate a release indicator which indicates that the SGsassociation is deactivated in the VLR, and to transmit the releaseindicator to the MME over the SGs interface.
 16. The system of claim 15wherein: the VLR is further configured to insert the release indicatorin a new Information Element (IE) of a message defined for the SGsinterface.
 17. The system of claim 16 wherein: the message defined forthe SGs interface comprises an SGs-RELEASE-REQUEST.
 18. The system ofclaim 15 wherein: the VLR is further configured to, in responsedetermining the mobile device attached to the LTE network afterinitially attaching to the GPRS network, update MM data for the mobiledevice to activate an SGs association with the MME, and update the MMdata for the mobile device to deactivate a Gs association with the SGSN;the VLR is further configured to generate a release indicator whichindicates that the Gs association is deactivated in the VLR, and totransmit the release indicator to the SGSN over the Gs interface. 19.The system of claim 18 wherein: the VLR is further configured to insertthe release indicator in a new Information Element (IE) of a messagedefined for the Gs interface.
 20. The system of claim 19 wherein: themessage defined for the Gs interface comprises a Gs-RELEASE-REQUEST.